Equity Premium: - Does it exist? Evidence from Germany and...
Transcript of Equity Premium: - Does it exist? Evidence from Germany and...
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Equity Premium: - Does it exist? Evidence from Germany and United Kingdom
Michael E. Drew Mirela Mallin
Tony Naughton and
Madhu Veeraraghavan
Discussion Paper No. 170, January 2004
Series edited by Associate Professor Andrew C Worthington
School of Economics and Finance
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Equity Premium: Does it exist? Evidence from Germany
and United Kingdom
Michael E. Drew Mirela Mallin
Tony Naughton and
Madhu Veeraraghavan
School of Economics and Finance Queensland University of Technology GPO Box 2434 Brisbane Queensland 4001 Australia School of Accounting and Finance Griffith University PMB 50 Gold Coast Mail Centre Gold Coast Queensland 9726 Australia School of Economics and Finance RMIT City Campus GPO Box 2476V Melbourne 3001 Australia Department of Accounting and Finance The University of Auckland Business School Private Bag 92019, Auckland, New Zealand
Abstract
Malkiel and Xu (1997) state that idiosyncratic volatility is highly correlated with size
and that it plays a powerful role in explaining expected returns. In this paper we ask
(a) whether idiosyncratic volatility is useful in explaining the variation in expected
returns; and, (b) whether our findings can be explained by the turn of the year effect.
We find that (a) our three-factor model provides a better description of expected
returns than the CAPM. That is, we find that firm size and idiosyncratic volatility are
related to security returns. In addition, we also find that our findings are robust
throughout the sample period. We show that the CAPM beta alone is not sufficient to
explain the variation in stock returns.
JEL Classification: G110, G120, G150
Keywords: Idiosyncratic Volatility, Size Effect, CAPM, Risk Premia
1. Introduction
Why has the rate of return on equities been higher than the rate of return on risk free
assets? The question first posed by Prescott and Mehra (1985) has been termed the
“equity premium puzzle”. One simple answer to this challenging question is that
equities are more risky than bonds and thus investors require a premium for taking
this additional risk. In the context of the Capital Asset Pricing Model [henceforth
CAPM] high beta stocks generate superior returns since there’s a linear relationship
between the stock’s beta and the expected return. However, recent tests show that
the cross-section of average stock returns shows little or no relation to the market
betas of the CAPM.
The results indicate that variables such as firm size1, leverage, firm’s book value of
equity to its market value, and more recently idiosyncratic volatility adequately
explain the cross-section of average stock returns better than the beta of a stock. In
an important paper Malkiel and Xu (1997) confirm the controversial finding of Fama
and French [hereafter FF] (1992) that beta does not appear as an explanatory
variable when attempting to model the annual returns on US stocks from 1963
through 1990.
They find that portfolios of smaller firms produce risk-adjusted rates of return that are
greater than the returns from portfolios of larger firms. Interestingly, they report that
1 Banz (1981) and Reinganum (1981) show that risk-adjusted stock returns are a monotonically
decreasing function of firm size. Banz (1981) shows that going long in a portfolio of small firms and
going short in a portfolio of big firms generates excess returns of approximately 20 percent per year.
Schultz (1983) shows that investors can earn risk-adjusted returns after transaction costs by holding
small firms for short periods. Also, see, Schwert (1983), Lakonishok and Smidt (1983), Chelley-Steeley
and Steeley (1996), Fletcher (1997), Priestley (1997), Heston et al (1999), Charitou et al (2001), Dimson
and Marsh (2001), Beltratti and Massimo (2002) and Dissanayake (2002).
idiosyncratic volatility is highly correlated with firm size and that it plays an important
role in explaining expected returns. That is, they observe that portfolios of smaller
companies have higher idiosyncratic volatility and thus these portfolios post
significantly higher average returns suggesting that asset returns are influenced by
factors that are not related to economic conditions. Finance theory states that
through the process of diversification “idiosyncratic factors” can be cancelled out and
thus asset returns are only influenced by systematic factors. In this article, we
advance this argument by providing out of sample evidence from two European stock
markets – Germany and United Kingdom.
We specifically ask:
(a) Is idiosyncratic volatility needed to explain the variation in average stock returns?
and,
(b) How are firm size and idiosyncratic volatility related to security returns?
We ask these two questions since recent research suggests that firm size is strongly
related to idiosyncratic volatility (Malkiel and Xu, 1997). Malkiel and Xu (1997) report
that portfolios of smaller stocks tend to have larger idiosyncratic volatility than
portfolios of larger stocks. More importantly, they show that idiosyncratic volatility is
highly correlated with firm size and that it plays a powerful role in explaining the
cross-section of expected returns. Malkiel and Xu (2000) report that idiosyncratic
volatility affects returns even after controlling for firm size and book-to-market equity
effects. They state that idiosyncratic volatility will affect asset returns when not every
investor is able to hold the market portfolio. Campbell, Lettau, Malkiel and Xu (2001)
find a noticeable increase in firm level volatility relative to the market volatility. Their
results indicate that firm specific volatility is the largest component of the total
volatility of an average firm. Xu and Malkiel (2001) report that volatility is associated
with the level of institutional ownership as well as a positive relationship between
idiosyncratic volatility and expected earnings growth. Drew and Veeraraghavan
(2002) show that small and high idiosyncratic volatility stocks generate superior
returns in Hong Kong, India, Malaysia and Philippines. Their findings support Malkiel
and Xu (1997 and 2000) who document that idiosyncratic risk is useful in explaining
the cross-section of expected returns.
Interestingly, Drew, Naughton and Veeraraghavan (2003) find that small and low
idiosyncratic volatility firms generate superior returns than big and high idiosyncratic
volatility firms for equities listed in Shanghai Stock Exchange. They propose a
behavioral explanation in that they forward irrational investor behavior as a possible
explanation in the spirit of Thaler (1999), Daniel and Titman (1999) and Hirshleifer
(2001). They conclude that Chinese investors are quasi-rational investors in the
sense of Thaler (1999).
Hamao, Mei and Xu (2002) state that the role of idiosyncratic risk in asset pricing has
largely been ignored since standard finance theory argues that only systematic risk
should be priced in the market. In a similar vein, Xu and Malkiel (2003) observe that
the behavior of idiosyncratic volatility has received far less attention in the finance
literature. This is because standard finance theory argues that idiosyncratic volatility
can be eliminated in a well-diversified portfolio. Barber and Odean (2000) and
Benartzi and Thaler (2001) report that both individual investors’ portfolios and mutual
fund portfolios’ are undiversified. Goyal and Santa-Clara (2001) argue that the lack of
diversification suggests that the relevant measure of risk for many investors may be
the total risk. It is important to note that little, if any, has been published on whether
idiosyncratic volatility can explain the cross section of expected stock returns.
In light of these discussions we investigate whether idiosyncratic volatility can serve
as a useful proxy for systematic risk and whether it helps explain the variation in
average stock returns for equities listed in German and United Kingdom markets.
The rest of the paper is organized as follows. Section 2 describes the data and
methodology employed in this paper. Section 3 presents our findings while Section 4
presents concluding comments.
2. Data and Methodology
2.1 Data and the model
We obtain monthly stock returns and market values of all listed firms in Germany and
United Kingdom covering the period 1991 to 2001 from DataStream. The relationship
between stock returns, overall market factor, size (ME), and idiosyncratic volatility is
investigated by employing the following model.
Rpt – Rft = apt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt +εpt [1]
Where, Rpt is the average return of a portfolio (S/L, S/M, S/H; B/L, B/M and B/H)2. Rft
is the risk-free rate3 observed at the beginning of each month. Market, is long the
market portfolio and short the risk free asset; SMB, is long small capitalization stocks
and short large capitalization stocks; HIVMLIV, is long high idiosyncratic volatility
2 S/L Portfolio = Small firms with low idiosyncratic volatility
S/M Portfolio = Small firms with medium idiosyncratic volatility
S/H Portfolio = Small firms with high idiosyncratic volatility
B/L Portfolio = Big firms with low idiosyncratic volatility
B/M Portfolio = Big firms with medium idiosyncratic volatility
B/H Portfolio = Big firms with high idiosyncratic volatility
3 We use the Germany Benchmark bond 10-year yield for Germany and the 1-month interbank rate for
United Kingdom as risk-free rate of return.
stocks and short low idiosyncratic volatility stocks. The factor loadings bp, sp and hp
are the slopes in the time-series regression.
2.2. Methodology
In this paper we follow the mimicking portfolio approach of FF (1996) in constructing
portfolios on firm size and idiosyncratic volatility. We follow this approach since
Malkiel and Xu (1997 and 2000), Xu and Malkiel (2001), Drew and Veeraraghavan
(2002b) and Drew, Naughton and Veeraraghavan (2003) suggest that idiosyncratic
volatility may be relevant for asset pricing and that it may serve as a useful proxy for
systematic risk.
Size Portfolios
At the end of December of each year t stocks are assigned to two portfolios of size
(Small or Big) based on whether their December market equity (ME) [defined as the
product of the closing price times number of shares outstanding] is above or below
the median ME. We form portfolios as of December of each year since most firms in
Germany have December as fiscal year end. For firms listed in United Kingdom size
portfolios are constructed at the end of March of each year since most firms have
March as fiscal year end.
Idiosyncratic Volatility Portfolios
In an independent sort the same stocks are allocated to three idiosyncratic volatility
portfolios (Low, Medium, and High) based on the breakpoints for the bottom 33.33
percent and top 66.67 percent. We first compute the variance of returns for each
stock in the sample. We define the variance of returns as the total risk of a stock. We
then estimate the beta for each stock by using the covariance / variance approach.
We define systematic risk as the beta of a stock multiplied by the variance of the
index. Note that we require the previous 24 months of average returns to calculate
the variance or beta of the stock. Stocks that do not have 24 months of continuous
returns are excluded from the sample. Similarly, we use the previous 24 months of
market returns to calculate the variance of the index. We define idiosyncratic volatility
as the difference between total risk and the systematic risk of a stock.
Six Intersection and three zero investment portfolios
We form six intersection and three zero investment portfolios. The six intersection
portfolios formed are (S/L, S/M, and S/H; B/L, B/M, and B/H). The three zero
investment portfolios are RMRFT, SMB and HIVMLIV. We define the three zero
investment portfolios RMRFT, SMB, and HIVMLIV as follows: RMRFT is long the
overall market portfolio and short the risk free asset. SMB (Small minus Big) is the
difference each month between the average of the returns of the three small stock
portfolios (S/L, S/M, and S/H) and the average of the returns of the three big
portfolios (B/L, B/M, and B/H). HIVMLIV (High Idiosyncratic Volatility minus Low
Idiosyncratic Volatility) is the difference between the average of the returns of the two
high idiosyncratic volatility portfolios (S/H, B/H) and the average of the returns on the
two low idiosyncratic volatility portfolios (S/L, B/L).
3. Results
3.1. Performance of the Intersection and Zero Cost Portfolios
Germany
Table 1.0 Sample Characteristics - Germany
Number of Companies in Portfolios Formed on Size and Idiosyncratic Volatility 1993 to 2001
YEAR S/L S/M S/H B/L B/M B/H Total
1993 16 21 9 37 12 7 102
1994 14 24 10 42 12 2 104
1995 16 23 9 45 8 4 105
1996 16 20 15 44 10 3 108
1997 14 22 16 43 13 5 113
1998 22 19 12 44 16 4 117
1999 22 26 5 42 23 3 121
2000 22 31 5 40 30 4 132
2001 29 26 15 40 38 7 155
Average 19 24 11 42 18 4 117
Table 1, reports the average numbers of firms in each portfolio for the sample period.
B/L portfolio has an average of 42 firms followed by the S/M portfolio with an average
of 24 firms. The S/L and B/M portfolios have an average of 19 and 18 firms
respectively. The least number of firms are in S/H and B/H portfolios with an average
of 11 and 4 respectively. Our first research question is to investigate whether a
multifactor asset-pricing model explains the cross-section of average stock returns.
Specifically, this study is interested in whether an overall market factor, firm size and
idiosyncratic volatility can explain the cross-sectional pattern of stock returns. The
mean monthly returns and the regression parameters are reported in Table 2.
Table 2.0
Summary Statistics and Multifactor Regressions for Portfolios Formed on Size and Idiosyncratic Volatility - Germany
1993-2001 Summary Statistics
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Panel A: Summary Statistics
Means Standard Deviations
Small 0.46 0.83 1.61 3.94 4.45 4.92
Big 0.52 0.76 1.10 4.38 3.73 8.38
Table 2, Panel A, shows the summary statistics while Panel B shows the regression
coefficients of the three-factor model. Our results show that all six portfolios generate
positive returns with the S/H portfolio generating the highest return of 1.61 per cent
per month. The overall performance of the six portfolios is graphically shown in figure
1.0. Our findings also show that the overall market factor generates a return of 0.52
per cent per month while the other two mimic portfolios, SMB and HIVMLIV generate
a return of 0.17 per cent per month and 0.87 per cent per month respectively. Since,
the mimic portfolios for size and idiosyncratic volatility generate superior returns; we
argue that this is a compensation for risk not captured by the CAPM. That is, we
advance a risk-based explanation and suggest that small and high idiosyncratic
volatility firms are riskier than big and low idiosyncratic volatility firms.
Table 2 - Continued Multifactor Regressions for Portfolios Formed on Size and Idiosyncratic Volatility
Regression Coefficients
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Panel B: Rpt – Rft = apt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt +εit
a t (a)
Small 0.000 0.003 0.002 0.353 1.106 1.352
Big 0.002 0.004 0.000 1.028 1.898 0.076
b t(b)
Small 0.541 0.587 0.680 11.626 11.205 17.803
Big 0.708 0.531 0.569 18.377 12.250 10.172
s t(s)
Small 0.311 0.454 1.349 4.751 6.161 25.111
Big 0.103 -0.052 -0.935 1.899 -0.856 -11.874
h t(h)
Small 0.037 0.145 0.853 0.712 2.458 19.807
Big -0.097 0.047 1.086 -2.239 0.957 17.213
R2 s(e)
Small 0.65 0.68 0.91 2.57 2.89 2.11
Big 0.76 0.69 0.86 2.13 2.39 3.09
DW
Small 1.96 1.96 1.99
Big 1.92 1.93 1.98
Panel B, shows, that the intercept, is statistically insignificant and close to zero for all
six portfolios. The findings also show that the b coefficient is positive and highly
significant for the six portfolios. The s coefficient increases monotonically and is
positive and highly significant for the three small stock portfolios. As far as three big
portfolios are concerned the s coefficient is positive for B/L but negative for B/M and
B/H portfolios.
Note that our findings are consistent with that of FF (1996) who argues that small
firms load positively on SMB while big firms load negatively on SMB. The h
coefficient increases monotonically for all six portfolios and is highly significant at the
1% level for S/H and B/H portfolios. The other portfolios display low levels of
statistical significance. We do not find any evidence of autocorrelation since the d-
statistic close to 2 for all six portfolios. Similarly, the test for multicollinearity shows
no evidence of multicollinearity between the independent variables.
Insert Figure 1.0 about here
United Kingdom
Table 3.0
Sample Characteristics – United Kingdom Number of Companies In Portfolios Formed on Size and Idiosyncratic Volatility
1993 to 2001 YEAR S/L S/M S/H B/L B/M B/H Total
1993 41 130 204 204 117 40 736
1994 36 128 207 214 125 41 751
1995 39 113 215 218 149 41 775
1996 40 134 209 241 152 71 847
1997 68 148 215 239 164 93 927
1998 101 144 242 246 208 102 1043
1999 138 178 241 248 213 137 1155
2000 140 198 252 273 224 149 1236
2001 134 187 285 295 257 133 1291
Average 82 151 230 242 179 90 973
Table 3, reports the average number of firms in each portfolio for the sample period.
The B/L portfolio has the largest number of firms with an average of 242, followed
closely by the S/H portfolio with an average of 230 firms. The S/M portfolio contains
an average of 151 firms while B/M contains an average of 179 firms. The S/L and
B/H portfolios have an average of 82 and 90 firms respectively. In Table 4.0 we
report the summary statistics and regression coefficients of our multifactor model.
Panel A, shows, the summary statistics while Panel B shows the regression
coefficients.
Table 4.0
Summary Statistics and Multifactor Regressions for Portfolios Formed on Size and Idiosyncratic Volatility – United Kingdom
1993-2001 Summary Statistics
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Panel A: Summary Statistics
Means Standard Deviations
Small -0.18 -0.01 1.16 2.02 3.07 6.91
Big 0.79 0.18 3.36 4.09 3.40 8.89
Our results show that with the exception of two portfolios all other portfolios generate
positive returns. Our results also show that the B/H portfolio generates the highest
return of 3.36 per cent per month while the S/H portfolio generates a return of 1.16
per cent per month. Our findings for United Kingdom differ in this respect with that of
Germany where we found that the small and high idiosyncratic volatility portfolios
generate the highest returns.
The overall performance of the six portfolios is graphically shown in figure 2.0. Our
findings also show that the overall market factor generates a mean monthly return of
0.32 per cent per month while the mimic portfolio for size and idiosyncratic volatility
generate a return of –1.46 per cent per month and 1.96 per cent per month
respectively. Thus, in the case of United Kingdom we document a big firm effect.
Note that in Germany we found a small firm effect. However, it is to be noted that in
both the markets investigated in this paper we document an idiosyncratic volatility
effect. That is, portfolios with high idiosyncratic volatility firms generate higher returns
than portfolios with low idiosyncratic volatility firms.
Table 4 - Continued
Multifactor Regressions for Portfolios Formed on Size and Idiosyncratic Volatility Regression Coefficients
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Panel B: Rpt – Rft = apt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt +εit
a t (a)
Small -0.002 -0.004 0.001 -1.444 -1.464 0.385
Big -0.000 -0.001 0.004 -0.171 -0.299 2.200
b t(b)
Small 0.306 0.391 0.549 5.949 5.331 7.196
Big 0.525 0.440 0.281 8.459 5.976 5.378
s t(s)
Small 0.106 0.101 0.714 1.129 0.754 5.129
Big -0.452 -0.565 -1.063 -3.989 -3.495 -11.148
h t(h)
Small 0.089 0.225 0.975 3.479 6.161 25.612
Big 0.004 0.167 1.118 0.123 3.793 42.925
R2 s(e)
Small 0.72 0.65 0.88 2.63 2.32 2.41
Big 0.67 0.69 0.96 1.96 2.39 1.65
DW
Small 1.99 1.98 1.96
Big 1.97 2.07 1.96
In Table 4, Panel B, we report the coefficients of our multifactor model. Our findings
show that the intercept, a coefficient, is indistinguishable from zero for all six
portfolios. The b coefficient is positive and statistically significant for all portfolios.
The s coefficient is positive for the three small stock portfolios and statistically
significant only for S/H portfolio, while the big stock portfolios show negative
coefficients with statistical significance. The h coefficient increases monotonically for
all six portfolios and is highly significant at the 1% level for five out of six portfolios.
As far as the diagnostics are concerned we find no evidence of autocorrelation or
multi-collinearity in our sample.
Insert Figure 2.0 about here
3.2 Results from turn of the year effect
Germany
Prior research on the behaviour of stock prices documents a strong seasonality effect
occurring in the month of January, especially for small size stocks. This effect has
been described as the January effect. Research also shows that monthly seasonality
is linked to the size of the firm. Therefore, a natural extension to the size effect is to
examine whether it displays monthly seasonality. Thus, we ask whether multifactor
models findings can be explained by the turn of the year effect. In this model we add
a dummy variable that takes the value “1” for the month of January and “0” for
remaining months. Our model takes the following form:
Rpt – Rft = αpt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt + γpDJANt+ εt
Table 5.0
Tests for Turn of the Year Effect – Germany
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Rpt – Rft = apt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt + γp Jant+ εit
a t (a)
Small 0.001 0.003 0.002 0.377 1.214 1.293
Big 0.002 0.004 0.000 1.018 1.940 0.130
b t(b)
Small 0.542 0.589 0.680 11.538 11.172 17.650
Big 0.708 0.532 0.570 18.230 12.195 10.103
s t(s)
Small 0.309 0.446 1.349 4.613 5.919 24.518
Big 0.102 -0.057 -0.938 1.830 -0.923 -11.636
h t(h)
Small 0.037 0.146 0.853 0.711 2.461 19.707
Big -0.097 0.047 1.087 -2.225 0.963 17.133
γ t(γ)
Small -0.001 -0.005 -0.000 -0.138 -0.551 0.853
Big -0.000 -0.003 -0.002 -0.129 -0.448 -0.200
R2 s(e)
Small 0.57 0.59 0.91 2.58 2.90 2.12
Big 0.76 0.59 0.86 2.14 2.40 3.10
DW
Small 1.97 1.95 1.98
Big 2.05 1.94 2.02
Table 5, shows the regression coefficients for the multifactor model. Our findings do
not reveal any evidence of the turn of the year effect for Germany since the
coefficient for the January dummy is not statistically significant for any of the six
portfolios. Thus, we reject the claim that the multifactor model results can be
explained by the seasonality effect.
United Kingdom
In the case of United Kingdom we test for both January and April effects. In this
model January dummy is represented by γ while April dummy is represented by θ.
Our time-series model takes the following form:
Rpt – Rft = αpt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt + γpDJANt+ θpDAPRILt + εpt
Table 6
Tests for Turn of the Year Effect (January and April) – United Kingdom
Idiosyncratic Volatility Portfolios
Size Low Medium High Low Medium High
Rpt – Rft = apt + bp (Rmt-Rft) + spSMBt + hpHIVMLIVt + γp Jant+ θpFebt+εit
a t (a)
Small -0.002 -0.003 0.000 -0.950 -1.243 0.113
Big -0.000 -0.001 -0.003 -0.331 -0.365 -1.524
b t(b)
Small 0.312 0.396 0.557 5.969 5.274 7.194
Big 0.530 0.450 0.284 8.389 4.986 5.406
s t(s)
Small 0.100 0.100 0.731 1.063 0.738 5.216
Big -0.442 -0.552 -1.075 -3.862 -3.383 11.310
h t(h)
Small 0.087 0.225 0.981 3.361 6.047 25.538
Big 0.007 0.172 1.114 0.237 3.837 42.744
γ t(γ)
Small -0.004 -0.001 0.011 -0.801 -0.119 1.283
Big 0.006 0.008 -0.009 0.946 0.778 -1.551
θ t(θ)
Small -0.006 -0.0047 -0.000 -1.080 -0.461 -0.072
Big 0.006 0.008 -0.009 0.946 0.778 -1.551
R2 s(e)
Small 0.67 0.69 0.88 1.63 2.34 2.42
Big 0.64 0.66 0.92 1.97 2.82 1.64
DW
Small 1.99 1.98 1.97
Big 1.98 2.07 1.96
Once again, our findings reveal no evidence of the turn of the year effect since the
January and April dummy are statistically significant for any of the six portfolios.
Thus, we argue that the multifactor model is robust throughout the sample period.
We also do not find any evidence of autocorrelation or multicollinearity in our sample.
3.3 Factors of risk and risk premia
Germany
Table 7.0 Market, Size and Idiosyncratic Volatility Premia – Germany
Portfolio Market Premium
(%)
Size
Premium (%)
Idiosyncratic Volatility
Premium (%)
S/L 0.28 (11.626)
0.05 (4.751)
0.032 (0.712)
S/M 0.30 (11.205)
0.07 (6.161)
0.39 (2.458)
S/H 0.35 (17.803)
0.22 (25.111)
0.74 (19.807)
B/L 0.36 (18.377)
0.01 (1.899)
-0.08 (-2.239)
B/M 0.27 (12.250)
-0.00 (-0.856)
0.04 (0.957)
B/H 0.29 (10.172)
-0.15 (-11.874)
0.94 (17.213)
Our findings show that the market portfolio generates positive risk premia for all six
portfolios. We find that the (B/L) portfolio generates the highest risk premia of 0.36
percent per month (t-statistic = 18.377). We also report that idiosyncratic volatility is
highly correlated with firm size. Once again, we find that the (S/H) portfolio generates
the highest size premium of 0.22 per cent per month (t-statistic = 25.111) while the
(B/H) portfolio generates the highest idiosyncratic volatility premia of 0.94 per cent
per month (t-statistic = 17.213). We also observe that the premia associated with
idiosyncratic volatility increases monotonically for the three small and big stock
portfolios. As, small and high idiosyncratic volatility firms generate higher risk premia
we argue that these factors are compensation for the risk missed by the CAPM. Once
again our findings are consistent with that of Malkiel and Xu (1997 and 2000). Our
results are summarized in Figure 3.0.
Insert Figure 3.0 about here
United Kingdom
Table 8.0
Market, Size and Idiosyncratic Volatility Premia – United Kingdom
Portfolio Market
Premium (%)
Size
Premium (%)
Idiosyncratic Volatility
Premium (%)
S/L 0.09 (5.949)
-0.15 (1.129)
0.17 (3.479)
S/M 0.12 (5.331)
-0.15 (0.754)
0.44 (6.161)
S/H 0.17 (7.196)
-1.04 (5.129)
1.91 (25.612)
B/L 0.16 (8.459)
0.65 (-3.989)
0.01 (0.123)
B/M 0.14 (4.976)
0.82 (-3.495)
0.33 (3.793)
B/H 0.08 (5.378)
1.55 (-11.148)
2.19 (42.925)
Our findings reveal that the market factor generates positive risk premia for all six
portfolios. As with Germany we find that the (S/H) portfolio generates the highest risk
premia of 0.17 percent per month (t-statistic = 7.196). Interestingly, our findings for
United Kingdom are different from that of Germany in that we document a big firm
effect in UK. This is because we find that the three small stock portfolios generate
negative risk premia while the three big stock portfolios generate positive risk premia.
We observe that the (B/H) portfolio generates the highest size premia of 1.55 percent
per month (t-statistic = 11.148). As far as idiosyncratic volatility premia is concerned
we see a monotonic increase for all six portfolios. We find that the (B/H) portfolio
generates the highest premia of 2.19 percent per month (t-statistic = 42.925) followed
by the (S/H) portfolio of 1.91 percent per month (t-statistic = 25.612). The findings in
this respect are consistent with that of Germany. We suggest that if investors are
willing to take additional risks they should invest in firms with such characteristics.
We summarize these results in Figure 4.0.
Insert Figure 4.0 about here
4. Conclusions
The Capital Asset Pricing Model states that expected returns on securities are a
positive linear function of their market betas. However, Malkiel and Xu (1997 and
2000) contradict the CAPM by observing that idiosyncratic volatility is priced in the
market and hence related to stock returns. In this paper we ask (a) whether
idiosyncratic volatility is correlated with firm size and is it useful in explaining the
variation in stock returns; and, (b) whether our three-factor model findings can be
explained by the turn of the year effect.
Our findings suggest that idiosyncratic volatility is highly correlated with firm size and
that it is useful in explaining expected stock returns. In Tables 7 and 8 we present the
premia generated by market, firm size and idiosyncratic volatility for Germany and
United Kingdom. We find that small firms generate higher returns because they have
high idiosyncratic volatility. Thus, we argue that idiosyncratic volatility is correlated
with firm size. Interestingly, for UK we find that big firms have higher idiosyncratic
volatility and thus those portfolios generate superior returns. Hence, we advance the
argument that investors who invest in stocks with these characteristics tend to take
greater risk and thus higher risk premia are compensation for these risks. As far as
the seasonality issue is concerned we do not find any evidence of our results being
explained by the turn of the year effect. Our findings are consistent with Malkiel and
Xu (1997 and 2000) who find that idiosyncratic volatility is useful in explaining cross-
sectional expected returns. They also observe that idiosyncratic volatility is related to
the size of the firm in that small firms have high idiosyncratic volatility thus providing
an alternative explanation to the FF (1992) conclusions. Thus, we demonstrate that
idiosyncratic volatility plays an important role in empirical asset pricing. In closing, we
argue that the CAPM beta alone is not sufficient to describe the variation in average
equity returns.
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2
Figure 1.0 Mean Monthly Returns Germany
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
S/L S/M S/H B/L B/M B/H
Portfolios
Mon
thly
Ret
urns
(%)
3
Figure 2.0 Mean Monthly Returns United Kingdom
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
S/L S/M S/H B/L B/M B/H
Portfolios
Mon
thly
Ret
urns
(%)
4
Figure 3.0 Market, Size and Idiosyncratic Volatility PremiaGermany
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
S/L S/M S/H B/L B/M B/H
Portfolios
Mon
thly
Pre
mia
(%)
MARKETSIZEIDIO RISK
5
Figure 4.0 Market, Size and Idiosyncratic Volatility PremiaUnited Kingdom
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
S/L S/M S/H B/L B/M B/H
Portfolios
Mon
thly
Pre
mia
(%)
MARKETSIZEIDIO RISK